Temperature control devices for controlling the temperature of an object substance, which needs to be temperature controlled, such as a sheet mounted on one of an optical communication device, a medical apparatus, and a wheeled vehicle (see Japanese Laid-open Patent Publication No. 07-20950) have been conventionally available. Such a temperature control device is briefly described with reference to FIG. 3A, FIG. 3B, FIG. 4A and FIG. 4B. FIG. 3A and FIG. 3B illustrate a structure of a conventional temperature control device 10. FIG. 4A and FIG. 4B illustrate a structure of a Peltier device 50.
As illustrated in FIG. 3A and FIG. 3B, the conventional temperature control device 10 includes a Pulse Width Modulator (PWM) 20, a first low-pass filter 31, a second low-pass filter 32, and a Peltier device 50. Each of the first low-pass filter and the second low-pass filter 32 is arranged and connected between the PWM 20 and the Peltier device 50 in a state that allows a current output from the PWM 20 to be conducted therethrough, and removes an alternating current component contained in the current output from the PWM 20.
The conventional temperature control device 10 then heats an object substance 58, arranged next to the Peltier device 50, with the Peltier device 50 when the current output from the PWM 20 in a predetermined direction (for example, an X direction) flows through the first low-pass filter 31, the Peltier device 50, and the second low-pass filter 32 in that order as shown in a portion FIG. 3A.
More in detail, the conventional temperature control device 10 causes the current output from the PWM 20 in the predetermined direction (for example, in the X direction) to flow through a p-type lower electrode 55, a p-type semiconductor 53, an upper electrode 52, an n-type semiconductor 54, and an n-type lower electrode 56 in that order in the Peltier device 50 as shown in a portion FIG. 4A. The conventional temperature control device 10 then absorbs heat via a lower substrate 57, and discharges heat via an upper substrate 51, by means of holes in the p-type semiconductor 53 and electrons in the n-type semiconductor 54, thereby heating an object substance 58 arranged adjacent to the upper substrate 51.
A heating efficiency of the Peltier device 50 is now discussed further. A magnitude of the current flowing in the X direction is represented by the following equation (1). Here, “I” represents the magnitude of the current. Also, “I(0)” represents the magnitude of a direct current component of the “I.” Further, “A(n)” and “B(n) represent coefficients of an alternating current component of the “I.” Further, “n” represents a natural number. Further, “ω” represents an angular frequency. Further, “t” represents a time length. Further, “Σ” represent a sequence of numbers with respect to “n.” Further, “*” represents a multiplication operation.I=I0+Σ(A(n)*sin(nωt)+B(n)*cos(nωt)  (1)
Then, it can be assumed that equation (2) including equation (2-1), equation (2-2), and equation (2-3) holds true. Here, “n(1)” and “n(2)” represent predetermined natural numbers.
                    {                                                                            ⁢                                                      ∫                                                                  sin                        ⁡                                                  (                                                      n                            ⁢                                                                                                                  ⁢                            ω                            ⁢                                                                                                                  ⁢                            t                                                    )                                                                    ⁢                                              ⅆ                        t                                                                              =                  0                                                                                    (                                  2                  ⁢                                      -                                    ⁢                  1                                )                                                                                                        ⁢                                                      ∫                                                                  cos                        ⁡                                                  (                                                      n                            ⁢                                                                                                                  ⁢                            ω                            ⁢                                                                                                                  ⁢                            t                                                    )                                                                    ⁢                                              ⅆ                        t                                                                              =                  0                                                                                    (                                  2                  ⁢                                      -                                    ⁢                  2                                )                                                                                                        ⁢                                                      ∫                                                                  sin                        ⁡                                                  (                                                                                    n                              ⁡                                                              (                                1                                )                                                                                      ⁢                            ω                            ⁢                                                                                                                  ⁢                            t                                                    )                                                                    *                                              cos                        ⁡                                                  (                                                                                    n                              ⁡                                                              (                                2                                )                                                                                      ⁢                            ω                            ⁢                                                                                                                  ⁢                            t                                                    )                                                                    ⁢                                              ⅆ                        t                                                                              =                  0                                                                                    (                                  2                  ⁢                                      -                                    ⁢                  3                                )                                                                        (        2        )            
Equation (1) is integrated with reference to t of from “0 (zero)” to “τ” sufficiently large in comparison with “I”, and then if equation (2) is substituted into the integration results, equation (3) including the following equations (3-1) and (3-2) are calculated.
                    {                                                                            ⁢                                                      ∫                                          I                      ⁢                                              ⅆ                        t                                                                              =                                                            I                      0                                        ⁢                    τ                                                                                                      (                                  3                  ⁢                                      -                                    ⁢                  1                                )                                                                                                        ⁢                                                      ∫                                                                  I                        2                                            ⁢                                              ⅆ                        t                                                                              =                                                            (                                                                        I                          0                          2                                                +                                                                              Σ                            ⁡                                                          (                                                                                                A                                  ⁡                                                                      (                                    n                                    )                                                                                                  /                                                                  2                                                                                            )                                                                                2                                                +                                                                              Σ                            ⁡                                                          (                                                                                                B                                  ⁡                                                                      (                                    n                                    )                                                                                                  /                                                                  2                                                                                            )                                                                                2                                                                    )                                        ⁢                    τ                                                                                                      (                                  3                  ⁢                                      -                                    ⁢                  2                                )                                                                        (        3        )            
Also, a relationship between an amount of heat added by the Peltier device 50 and the magnitude of the current is represented by the following equation (4). Here, “Q(x)” represents the heat added. Further, “Π(pi)” represents a Peltier coefficient. Further, “S” represents a thermal resistance when heat is absorbed via the lower substrate 57 and when heat is discharged via the upper substrate 51. Further, “ΔT” represents a temperature difference between the upper substrate 51 and the lower substrate 57. Further, “R” represents an electrical resistance of the Peltier device 50.Q(x)=Π*I−ST+(½)I2R  (4)
If equation (4) is integrated with respect to t from “0 (zero)” to “τ,” the following equation (5) results from equation (4).∫Q(x)dt=Π*∫Idt−STτ+(½)R*∫I2dt  (5)
If equation (3) is substituted in equation (5), equation (5) may be modified into the following equation (6).
                                          (                          1              /              τ                        )                    ⁢                      ∫                                          Q                ⁡                                  (                  x                  )                                            ⁢                              ⅆ                t                                                    =                              Π            *                          I              0                                -                      S            ⁢                        ⁢            T                    +                                                    (                                  1                  /                  2                                )                            ⁢              R              *                              (                                                      I                    0                    2                                    +                                                            Σ                      ⁡                                              (                                                                              A                            ⁡                                                          (                              n                              )                                                                                /                                                      2                                                                          )                                                              2                                    +                                                            Σ                      ⁡                                              (                                                                              B                            ⁡                                                          (                              n                              )                                                                                /                                                      2                                                                          )                                                              2                                                  )                                                    Third              ⁢                                                          ⁢              term              ⁢                                                          ⁢              on              ⁢                                                          ⁢              the              ⁢                                                          ⁢              right              ⁢                                                          ⁢              side                                                          (        6        )            
A third term of the right side of equation (6) means that the Joule heat caused by the alternating current component (heat generation caused by the electrical resistance) is contained. More specifically, when the object substance 58 is heated by the Peltier device 50, the alternating current component contained in the current flowing in the X direction contributes to the heating efficiency.
On the other hand, the conventional temperature control device 10 cools the object substance 58, arranged adjacent to the Peltier device 50, with the Peltier device 50 if a current output from the PWM 20 in a direction opposite from the predetermined direction (for example, in a Y direction) is conducted through the second low-pass filter 32, the Peltier device 50, and the first low-pass filter 31 in that order as shown in a portion FIG. 3B.
More in detail, the conventional temperature control device 10 causes the current to flow through the n-type lower electrode 56, the n-type semiconductor 54, the upper electrode 52, the p-type semiconductor 53, and the p-type lower electrode 55 in that order in the Peltier device 50 in the opposite direction from the PWM 20 opposite from the predetermined direction (for example, in the Y direction) as shown in a portion FIG. 4B. In this case, the conventional temperature control device 10 discharges heat via the lower substrate 57 and absorbs heat via the upper substrate 51 by means of holes in the p-type semiconductor 53 and electrons in the n-type semiconductor 54, thereby cooling the object substance 58 arranged adjacent to the upper substrate 51.
A cooling efficiency of the Peltier device 50 is also described. A relationship between an amount of heat absorbed by the Peltier device 50 and a magnitude of a current is represented by the following equation (7). Here, “Q(y)” represents the absorbed heat amount.∫Q(y)dt=Π*∫I−STτ−(½)R*∫I2dt  (7)
In the same manner as described with reference to the heating efficiency of the Peltier device 50, equation (7) may be modified into the following equation (8).
                                          (                          1              /              τ                        )                    ⁢                      ∫                                          Q                ⁡                                  (                  y                  )                                            ⁢                              ⅆ                t                                                    =                              Π            *                          I              ⁡                              (                0                )                                              -                      S            ⁢                        ⁢            T                    -                                                    (                                  1                  /                  2                                )                            ⁢              R              *                              (                                                      I                    0                    2                                    +                                                            Σ                      ⁡                                              (                                                                              A                            ⁡                                                          (                              n                              )                                                                                /                                                      2                                                                          )                                                              2                                    +                                                            Σ                      ⁡                                              (                                                                              B                            ⁡                                                          (                              n                              )                                                                                /                                                      2                                                                          )                                                              2                                                  )                                                    Third              ⁢                                                          ⁢              term              ⁢                                                          ⁢              on              ⁢                                                          ⁢              the              ⁢                                                          ⁢              right              ⁢                                                          ⁢              side                                                          (        8        )            
A third term of equation (8) means that the Joule heat caused by an alternating current component is contained. More specifically, when an object substance 58 is cooled by the Peltier device 50, the alternating current component contained in the current flowing in the Y direction means a drop in the cooling efficiency.
The related art described above has a problem that the alternating current component contained in the current is not effectively used. More specifically, the conventional temperature control device 10 has a problem that since the conventional temperature control device 10 typically has an apparatus structure including a low-pass filter, the alternating current component contained in the current is removed and the alternating current component contributing to the heating efficiency is not effectively used.